grpc-json: add option to convert gRPC status into JSON body (#3383)

api/envoy/config/filter/http/transcoder/v2/transcoder.proto

@@ -120,4 +120,34 @@ message GrpcJsonTranscoder {
   // not know them beforehand. Otherwise use ``ignored_query_parameters``.
   // Defaults to false.
   bool ignore_unknown_query_parameters = 8;
+
+  // Whether to convert gRPC status headers to JSON.
+  // When trailer indicates a gRPC error and there was no HTTP body, take ``google.rpc.Status``
+  // from the ``grpc-status-details-bin`` header and use it as JSON body.
+  // If there was no such header, make ``google.rpc.Status`` out of the ``grpc-status`` and
+  // ``grpc-message`` headers.
+  // The error details types must be present in the ``proto_descriptor``.
+  //
+  // For example, if an upstream server replies with headers:
+  //
+  // .. code-block:: none
+  //
+  //     grpc-status: 5
+  //     grpc-status-details-bin:
+  //         CAUaMwoqdHlwZS5nb29nbGVhcGlzLmNvbS9nb29nbGUucnBjLlJlcXVlc3RJbmZvEgUKA3ItMQ
+  //
+  // The ``grpc-status-details-bin`` header contains a base64-encoded protobuf message
+  // ``google.rpc.Status``. It will be transcoded into:
+  //
+  // .. code-block:: none
+  //
+  //     HTTP/1.1 404 Not Found
+  //     content-type: application/json
+  //
+  //     {"code":5,"details":[{"@type":"type.googleapis.com/google.rpc.RequestInfo","requestId":"r-1"}]}
+  //
+  //  In order to transcode the message, the ``google.rpc.RequestInfo`` type from
+  //  the ``google/rpc/error_details.proto`` should be included in the configured
+  //  :ref:`proto descriptor set <config_grpc_json_generate_proto_descriptor_set>`.
+  bool convert_grpc_status = 9;
 }

docs/root/intro/version_history.rst

@@ -23,6 +23,7 @@ Version history
 * fault: added overrides for default runtime keys in :ref:`HTTPFault <envoy_api_msg_config.filter.http.fault.v2.HTTPFault>` filter.
 * grpc: added :ref:`AWS IAM grpc credentials extension <envoy_api_file_envoy/config/grpc_credential/v2alpha/aws_iam.proto>` for AWS-managed xDS.
 * grpc-json: added support for :ref:`ignoring unknown query parameters<envoy_api_field_config.filter.http.transcoder.v2.GrpcJsonTranscoder.ignore_unknown_query_parameters>`.
+* grpc-json: added support for :ref:`the grpc-status-details-bin header<envoy_api_field_config.filter.http.transcoder.v2.GrpcJsonTranscoder.convert_grpc_status>`.
 * header to metadata: added :ref:`PROTOBUF_VALUE <envoy_api_enum_value_config.filter.http.header_to_metadata.v2.Config.ValueType.PROTOBUF_VALUE>` and :ref:`ValueEncode <envoy_api_enum_config.filter.http.header_to_metadata.v2.Config.ValueEncode>` to support protobuf Value and Base64 encoding.
 * http: added the ability to reject HTTP/1.1 requests with invalid HTTP header values, using the runtime feature `envoy.reloadable_features.strict_header_validation`.
 * http: added the ability to :ref:`merge adjacent slashes<envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.merge_slashes>` in the path.

source/common/grpc/BUILD

@@ -86,6 +86,7 @@ envoy_cc_library(
         "//source/common/buffer:buffer_lib",
         "//source/common/buffer:zero_copy_input_stream_lib",
         "//source/common/common:assert_lib",
+        "//source/common/common:base64_lib",
         "//source/common/common:empty_string",
         "//source/common/common:enum_to_int",
         "//source/common/common:hash_lib",

source/common/grpc/common.cc

@@ -10,6 +10,7 @@
 #include "common/buffer/buffer_impl.h"
 #include "common/buffer/zero_copy_input_stream_impl.h"
 #include "common/common/assert.h"
+#include "common/common/base64.h"
 #include "common/common/empty_string.h"
 #include "common/common/enum_to_int.h"
 #include "common/common/fmt.h"
@@ -54,7 +55,7 @@ absl::optional<Status::GrpcStatus> Common::getGrpcStatus(const Http::HeaderMap&
 
   uint64_t grpc_status_code;
   if (!grpc_status_header || grpc_status_header->value().empty()) {
-    return {};
+    return absl::nullopt;
   }
   if (!absl::SimpleAtoi(grpc_status_header->value().getStringView(), &grpc_status_code) ||
       grpc_status_code > Status::GrpcStatus::MaximumValid) {
@@ -68,6 +69,27 @@ std::string Common::getGrpcMessage(const Http::HeaderMap& trailers) {
   return entry ? std::string(entry->value().getStringView()) : EMPTY_STRING;
 }
 
+absl::optional<google::rpc::Status>
+Common::getGrpcStatusDetailsBin(const Http::HeaderMap& trailers) {
+  const Http::HeaderEntry* details_header = trailers.get(Http::Headers::get().GrpcStatusDetailsBin);
+  if (!details_header) {
+    return absl::nullopt;
+  }
+
+  // Some implementations use non-padded base64 encoding for grpc-status-details-bin.
+  auto decoded_value = Base64::decodeWithoutPadding(details_header->value().getStringView());
+  if (decoded_value.empty()) {
+    return absl::nullopt;
+  }
+
+  google::rpc::Status status;
+  if (!status.ParseFromString(decoded_value)) {
+    return absl::nullopt;
+  }
+
+  return {std::move(status)};
+}
+
 Buffer::InstancePtr Common::serializeToGrpcFrame(const Protobuf::Message& message) {
   // http://www.grpc.io/docs/guides/wire.html
   // Reserve enough space for the entire message and the 5 byte header.

source/common/grpc/common.h

@@ -57,6 +57,15 @@ class Common {
    */
   static std::string getGrpcMessage(const Http::HeaderMap& trailers);
 
+  /**
+   * Returns the decoded google.rpc.Status message from a given set of trailers, if present.
+   * @param trailers the trailers to parse.
+   * @return std::unique_ptr<google::rpc::Status> the gRPC status message or empty pointer if no
+   *         grpc-status-details-bin trailer found or it was invalid.
+   */
+  static absl::optional<google::rpc::Status>
+  getGrpcStatusDetailsBin(const Http::HeaderMap& trailers);
+
   /**
    * Parse gRPC header 'grpc-timeout' value to a duration in milliseconds.
    * @param request_headers the header map from which to extract the value of 'grpc-timeout' header.

source/common/http/headers.h

@@ -123,6 +123,7 @@ class HeaderValues {
   const LowerCaseString GrpcStatus{"grpc-status"};
   const LowerCaseString GrpcTimeout{"grpc-timeout"};
   const LowerCaseString GrpcAcceptEncoding{"grpc-accept-encoding"};
+  const LowerCaseString GrpcStatusDetailsBin{"grpc-status-details-bin"};
   const LowerCaseString Host{":authority"};
   const LowerCaseString HostLegacy{"host"};
   const LowerCaseString KeepAlive{"keep-alive"};

source/common/protobuf/protobuf.h

@@ -7,6 +7,7 @@
 #include "google/protobuf/any.pb.h"
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/descriptor.pb.h"
+#include "google/protobuf/descriptor_database.h"
 #include "google/protobuf/empty.pb.h"
 #include "google/protobuf/io/coded_stream.h"
 #include "google/protobuf/io/zero_copy_stream.h"

source/extensions/filters/http/grpc_json_transcoder/json_transcoder_filter.cc

@@ -111,9 +111,13 @@ JsonTranscoderConfig::JsonTranscoderConfig(
   }
 
   for (const auto& file : descriptor_set.file()) {
-    if (descriptor_pool_.BuildFile(file) == nullptr) {
-      throw EnvoyException("transcoding_filter: Unable to build proto descriptor pool");
-    }
+    addFileDescriptor(file);
+  }
+
+  convert_grpc_status_ = proto_config.convert_grpc_status();
+  if (convert_grpc_status_) {
+    addBuiltinSymbolDescriptor("google.protobuf.Any");
+    addBuiltinSymbolDescriptor("google.rpc.Status");
   }
 
   PathMatcherBuilder<const Protobuf::MethodDescriptor*> pmb;
@@ -164,10 +168,34 @@ JsonTranscoderConfig::JsonTranscoderConfig(
   ignore_unknown_query_parameters_ = proto_config.ignore_unknown_query_parameters();
 }
 
+void JsonTranscoderConfig::addFileDescriptor(const Protobuf::FileDescriptorProto& file) {
+  if (descriptor_pool_.BuildFile(file) == nullptr) {
+    throw EnvoyException("transcoding_filter: Unable to build proto descriptor pool");
+  }
+}
+
+void JsonTranscoderConfig::addBuiltinSymbolDescriptor(const std::string& symbol_name) {
+  if (descriptor_pool_.FindFileContainingSymbol(symbol_name) != nullptr) {
+    return;
+  }
+
+  auto* builtin_pool = Protobuf::DescriptorPool::generated_pool();
+  if (!builtin_pool) {
+    return;
+  }
+
+  Protobuf::DescriptorPoolDatabase pool_database(*builtin_pool);
+  Protobuf::FileDescriptorProto file_proto;
+  pool_database.FindFileContainingSymbol(symbol_name, &file_proto);
+  addFileDescriptor(file_proto);
+}
+
 bool JsonTranscoderConfig::matchIncomingRequestInfo() const {
   return match_incoming_request_route_;
 }
 
+bool JsonTranscoderConfig::convertGrpcStatus() const { return convert_grpc_status_; }
+
 ProtobufUtil::Status JsonTranscoderConfig::createTranscoder(
     const Http::HeaderMap& headers, ZeroCopyInputStream& request_input,
     google::grpc::transcoding::TranscoderInputStream& response_input,
@@ -244,6 +272,14 @@ JsonTranscoderConfig::methodToRequestInfo(const Protobuf::MethodDescriptor* meth
   return ProtobufUtil::Status();
 }
 
+ProtobufUtil::Status
+JsonTranscoderConfig::translateProtoMessageToJson(const Protobuf::Message& message,
+                                                  std::string* json_out) {
+  return ProtobufUtil::BinaryToJsonString(
+      type_helper_->Resolver(), Grpc::Common::typeUrl(message.GetDescriptor()->full_name()),
+      message.SerializeAsString(), json_out, print_options_);
+}
+
 JsonTranscoderFilter::JsonTranscoderFilter(JsonTranscoderConfig& config) : config_(config) {}
 
 Http::FilterHeadersStatus JsonTranscoderFilter::decodeHeaders(Http::HeaderMap& headers,
@@ -385,6 +421,8 @@ Http::FilterDataStatus JsonTranscoderFilter::encodeData(Buffer::Instance& data,
     return Http::FilterDataStatus::Continue;
   }
 
+  has_body_ = true;
+
   // TODO(dio): Add support for streaming case.
   if (has_http_body_output_) {
     buildResponseFromHttpBodyOutput(*response_headers_, data);
@@ -420,25 +458,42 @@ Http::FilterTrailersStatus JsonTranscoderFilter::encodeTrailers(Http::HeaderMap&
 
   if (data.length()) {
     encoder_callbacks_->addEncodedData(data, true);
+    has_body_ = true;
   }
 
   if (method_->server_streaming()) {
     // For streaming case, the headers are already sent, so just continue here.
     return Http::FilterTrailersStatus::Continue;
   }
 
+  // If there was no previous headers frame, this |trailers| map is our |response_headers_|,
+  // so there is no need to copy headers from one to the other.
+  bool is_trailers_only_response = response_headers_ == &trailers;
+
   const absl::optional<Grpc::Status::GrpcStatus> grpc_status =
       Grpc::Common::getGrpcStatus(trailers);
+  bool status_converted_to_json = grpc_status && maybeConvertGrpcStatus(*grpc_status, trailers);
+
   if (!grpc_status || grpc_status.value() == Grpc::Status::GrpcStatus::InvalidCode) {
     response_headers_->Status()->value(enumToInt(Http::Code::ServiceUnavailable));
   } else {
     response_headers_->Status()->value(Grpc::Utility::grpcToHttpStatus(grpc_status.value()));
-    response_headers_->insertGrpcStatus().value(enumToInt(grpc_status.value()));
+    if (!status_converted_to_json && !is_trailers_only_response) {
+      response_headers_->insertGrpcStatus().value(enumToInt(grpc_status.value()));
+    }
   }
 
-  const Http::HeaderEntry* grpc_message_header = trailers.GrpcMessage();
-  if (grpc_message_header) {
-    response_headers_->insertGrpcMessage().value(*grpc_message_header);
+  if (status_converted_to_json && is_trailers_only_response) {
+    // Drop the gRPC status headers, we already have them in the JSON body.
+    response_headers_->removeGrpcStatus();
+    response_headers_->removeGrpcMessage();
+    response_headers_->remove(Http::Headers::get().GrpcStatusDetailsBin);
+  } else if (!status_converted_to_json && !is_trailers_only_response) {
+    // Copy the grpc-message header if it exists.
+    const Http::HeaderEntry* grpc_message_header = trailers.GrpcMessage();
+    if (grpc_message_header) {
+      response_headers_->insertGrpcMessage().value(*grpc_message_header);
+    }
   }
 
   // remove Trailer headers if the client connection was http/1
@@ -496,6 +551,56 @@ void JsonTranscoderFilter::buildResponseFromHttpBodyOutput(Http::HeaderMap& resp
   }
 }
 
+bool JsonTranscoderFilter::maybeConvertGrpcStatus(Grpc::Status::GrpcStatus grpc_status,
+                                                  Http::HeaderMap& trailers) {
+  if (!config_.convertGrpcStatus()) {
+    return false;
+  }
+
+  // We do not support responses with a separate trailer frame.
+  // TODO(ascheglov): remove this if after HCM can buffer data added from |encodeTrailers|.
+  if (response_headers_ != &trailers) {
+    return false;
+  }
+
+  // Send a serialized status only if there was no body.
+  if (has_body_) {
+    return false;
+  }
+
+  if (grpc_status == Grpc::Status::GrpcStatus::Ok ||
+      grpc_status == Grpc::Status::GrpcStatus::InvalidCode) {
+    return false;
+  }
+
+  auto status_details = Grpc::Common::getGrpcStatusDetailsBin(trailers);
+  if (!status_details) {
+    // If no rpc.Status object was sent in the grpc-status-details-bin header,
+    // construct it from the grpc-status and grpc-message headers.
+    status_details.emplace();
+    status_details->set_code(grpc_status);
+
+    auto grpc_message_header = trailers.GrpcMessage();
+    if (grpc_message_header) {
+      auto message = grpc_message_header->value().getStringView();
+      status_details->set_message(message.data(), message.size());
+    }
+  }
+
+  std::string json_status;
+  auto translate_status = config_.translateProtoMessageToJson(*status_details, &json_status);
+  if (!translate_status.ok()) {
+    ENVOY_LOG(debug, "Transcoding status error {}", translate_status.ToString());
+    return false;
+  }
+
+  response_headers_->insertContentType().value().setReference(
+      Http::Headers::get().ContentTypeValues.Json);
+  Buffer::OwnedImpl status_data(json_status);
+  encoder_callbacks_->addEncodedData(status_data, false);
+  return true;
+}
+
 bool JsonTranscoderFilter::hasHttpBodyAsOutputType() {
   return method_->output_type()->full_name() == google::api::HttpBody::descriptor()->full_name();
 }

source/extensions/filters/http/grpc_json_transcoder/json_transcoder_filter.h

@@ -68,13 +68,25 @@ class JsonTranscoderConfig : public Logger::Loggable<Logger::Id::config> {
                    std::unique_ptr<google::grpc::transcoding::Transcoder>& transcoder,
                    const Protobuf::MethodDescriptor*& method_descriptor);
 
+  /**
+   * Converts an arbitrary protobuf message to JSON.
+   */
+  ProtobufUtil::Status translateProtoMessageToJson(const Protobuf::Message& message,
+                                                   std::string* json_out);
+
   /**
    * If true, skip clearing the route cache after the incoming request has been modified.
    * This allows Envoy to select the upstream cluster based on the incoming request
    * rather than the outgoing.
    */
   bool matchIncomingRequestInfo() const;
 
+  /**
+   * If true, when trailer indicates a gRPC error and there was no HTTP body,
+   * make google.rpc.Status out of gRPC status headers and use it as JSON body.
+   */
+  bool convertGrpcStatus() const;
+
 private:
   /**
    * Convert method descriptor to RequestInfo that needed for transcoding library
@@ -83,13 +95,17 @@ class JsonTranscoderConfig : public Logger::Loggable<Logger::Id::config> {
                                            google::grpc::transcoding::RequestInfo* info);
 
 private:
+  void addFileDescriptor(const Protobuf::FileDescriptorProto& file);
+  void addBuiltinSymbolDescriptor(const std::string& symbol_name);
+
   Protobuf::DescriptorPool descriptor_pool_;
   google::grpc::transcoding::PathMatcherPtr<const Protobuf::MethodDescriptor*> path_matcher_;
   std::unique_ptr<google::grpc::transcoding::TypeHelper> type_helper_;
   Protobuf::util::JsonPrintOptions print_options_;
 
   bool match_incoming_request_route_{false};
   bool ignore_unknown_query_parameters_{false};
+  bool convert_grpc_status_{false};
 };
 
 using JsonTranscoderConfigSharedPtr = std::shared_ptr<JsonTranscoderConfig>;
@@ -125,6 +141,7 @@ class JsonTranscoderFilter : public Http::StreamFilter, public Logger::Loggable<
 private:
   bool readToBuffer(Protobuf::io::ZeroCopyInputStream& stream, Buffer::Instance& data);
   void buildResponseFromHttpBodyOutput(Http::HeaderMap& response_headers, Buffer::Instance& data);
+  bool maybeConvertGrpcStatus(Grpc::Status::GrpcStatus grpc_status, Http::HeaderMap& trailers);
   bool hasHttpBodyAsOutputType();
 
   JsonTranscoderConfig& config_;
@@ -139,6 +156,7 @@ class JsonTranscoderFilter : public Http::StreamFilter, public Logger::Loggable<
 
   bool error_{false};
   bool has_http_body_output_{false};
+  bool has_body_{false};
 };
 
 } // namespace GrpcJsonTranscoder

test/common/grpc/common_test.cc

@@ -78,6 +78,28 @@ TEST(GrpcContextTest, GetGrpcTimeout) {
   // so we don't test for them.
 }
 
+TEST(GrpcCommonTest, GrpcStatusDetailsBin) {
+  Http::TestHeaderMapImpl empty_trailers;
+  EXPECT_FALSE(Common::getGrpcStatusDetailsBin(empty_trailers));
+
+  Http::TestHeaderMapImpl invalid_value{{"grpc-status-details-bin", "invalid"}};
+  EXPECT_FALSE(Common::getGrpcStatusDetailsBin(invalid_value));
+
+  Http::TestHeaderMapImpl unpadded_value{
+      {"grpc-status-details-bin", "CAUSElJlc291cmNlIG5vdCBmb3VuZA"}};
+  auto status = Common::getGrpcStatusDetailsBin(unpadded_value);
+  ASSERT_TRUE(status);
+  EXPECT_EQ(Status::GrpcStatus::NotFound, status->code());
+  EXPECT_EQ("Resource not found", status->message());
+
+  Http::TestHeaderMapImpl padded_value{
+      {"grpc-status-details-bin", "CAUSElJlc291cmNlIG5vdCBmb3VuZA=="}};
+  status = Common::getGrpcStatusDetailsBin(padded_value);
+  ASSERT_TRUE(status);
+  EXPECT_EQ(Status::GrpcStatus::NotFound, status->code());
+  EXPECT_EQ("Resource not found", status->message());
+}
+
 TEST(GrpcContextTest, ToGrpcTimeout) {
   Http::HeaderString value;